1. Field of the Invention
This invention relates to an electrical circuit breaker of the type that main contacts provided across electric supply lines connected to a load are opened upon flow of an excessive current such as an overload current.
2. Description of the Prior Art
Conventional electrical circuit breakers of the above-described type comprise a current transformer for detecting an overcurrent, a control circuit generating an overcurrent trip signal based on a detection output of the current transformer, and a tripping device for opening the main contacts provided across the electric supply lines, via a switching mechanism. In these circuit breakers, the current transformer, the control circuit and the tripping device are disposed at respective positions away from the switching mechanism opening and closing the main contacts and nearer to terminals of the load side.
When the circuit breaker of the above-described type is employed for three-phase circuits, particularly, three current transformers with the electric supply lines to the load as respective primary conductors are provided since the detection of the overload current needs to be performed for the respective electric supply lines. The three transformers thus occupy concentrated positions in proximity to the load side terminals. In the above-described circuit breaker employed for the three-phase circuit, when a zero-phase-sequence current transformer is incorporated for addition of a function of an earth leakage breaker or when a control power transformer is incorporated, these are also disposed in proximity to the load side terminals. Consequently, the assembly of the circuit breaker is complicated and its compactness is prevented although that has been desired from the standpoint of secured distance for insulation.